Generally, fusion-splicing end faces of a pair of optical fibers to each other by discharge heating is carried out by holding the pair of optical fibers with holding units and by placing, positioning, and fixing parts of the optical fibers on the end-face sides of the holding units into V-grooves formed in V-groove blocks.
At this time, a virtual straight line joining a pair of discharge electrodes to each other and an axial center of the optical fibers are usually set to agree with each other. In this case, the holding units and V-groove blocks hold and fix the pair of optical fibers so that the axial center of the optical fibers agrees with the straight line that joins the pair of discharge electrodes to each other.
If the optical fibers have a low melting point, the fusion splicing thereof must avoid excessive fusion. This raises a necessity of slightly shifting the axial center of the pair of optical fibers from the virtual straight line that joins the pair of discharge electrodes to each other. To fulfill the necessity, only the V-groove blocks that are located in the vicinities of the splicing end faces of the optical fibers may be moved.
A known technique of shifting an axial center of optical fibers from a virtual straight line joining a pair of discharge electrodes and fusion-splicing the optical fibers is described in Japanese Patent Publication No. 2860831 (Patent Literature 1). A known technique of moving a V-groove block is described in Japanese Unexamined Patent Application Publication No. 2002-6167 (Patent Literature 2).